An Army buddy of Timothy McVeigh, the first suspect charged in the Oklahoma City bombing, has told federal authorities that he and McVeigh inspected the Alfred P. Murrah Federal Building there as a target several days before the blast, law-enforcement officials said Friday.

Michael Fortier, a close friend of McVeigh from their days together at Fort Riley, Kan., also told the authorities that McVeigh confided to him about plans for the bombing months earlier when McVeigh was with him in Kingman, Ariz., the officials said.

Fortier made the statements to federal prosecutors as part of negotiations toward a possible deal in which he may cooperate with the government, said the officials, who spoke on condition of anonymity.

Fortier said the two men drove from Arizona to the federal building in Oklahoma about a week before the bombing in a visit that officials said appeared to be a trip to inspect the nine-story building.

Fortier has denied that he had any direct role in the bombing. Nevertheless, the authorities have been intensely interested in him since the blast. They had questioned him and searched his trailer in Kingman and an adjoining storage shed, but had said they had no basis to suspect him of involvement.

The offer of cooperation could represent an important breakthrough in an investigation that has appeared stalled in recent weeks, with hundreds of federal agents working nationwide in a frustrating search for possible conspirators.

In addition to McVeigh, one other man, Terry Nichols, has been charged in the April 19 blast, which killed 166 people.

Fortier’s discussions with the government began after he was subpoenaed earlier this month to testify to a federal grand jury in Oklahoma City. Rather than testify under oath, Fortier apparently approached the government about a negotiated settlement and made his statements about McVeigh in an initial offer of the kind of evidence he could provide.

It is possible that he would seek full immunity from prosecution in return for his information, but prosecutors may be unlikely to accept such a deal from anyone with knowledge of the blast.